Best Spark Plugs For Harley Davidson – 7 Options Reviewed

When I first started wrenching on my Twin Cam, I realized quickly that seemingly small components, like the right set of Harley Davidson spark plugs, have a huge impact on overall engine performance and smooth throttle response. Choosing a premium plug can eliminate those annoying misfires and truly make your V-Twin sing, whether you’re cruising the highway or ripping through the gears. This hands-on guide compares the top seven highly-rated options for riders looking to maximize durability and ignitability in their motorcycles.

IMAGE	PRODUCT NAME	AMAZON LINK
	NGK Iridium IX DCPR7EIX Spark Plugs Compatible with…	View on Amazon
	2Pcs CNPAPC Upgrade Double Iridium IX Spark Plugs DCPR7EIX…	View on Amazon
	NGK CR9EIX – Iridium IX Spark Plug – 4-Pack/–	View on Amazon
	E3 Spark Plugs E3.36 Premium Powersports Spark Plug for…	View on Amazon
	NGK DCPR7EIX Spark Plug (2 Pack)	View on Amazon
	NGK # 6046 Iridium Spark Plugs — DCPR7EIX — Compatible…	View on Amazon
	NGK Iridium Sparkplug BPR5EIX-11 for Harley-Davidson Dyna…	View on Amazon

NGK Iridium IX DCPR7EIX Spark Plugs Compatible with 1999-2016 Harley Davidson Twin Cam (Pair)

If you ride a newer Twin Cam, the NGK Iridium IX series is often considered the benchmark upgrade for reliability and performance. These plugs are designed to provide a consistently powerful spark while demanding less voltage from your ignition system. They are an excellent drop-in replacement, requiring little to no adjustment right out of the box, making them a favorite among riders looking for hassle-free performance enhancement.

Key features that stand out:
* Come pre-gapped: Ready for installation in most compatible models.
* Ultra-small diameter center electrode: Reduces the necessary voltage for ignition.
* New metal shell plating: Enhanced anti-corrosion qualities for longer life.
* Industry leader performance: Trusted technology for consistent horsepower.

• Pros: Exceptional performance stability, improved cold starting, highly durable Iridium tip.
• Cons: They are generally more expensive than standard copper plugs.
• Best for: Riders of 1999-2016 Twin Cam models seeking a reliable, high-performance upgrade.

Expert Opinion: This is the go-to performance plug for modern Harley V-Twins. The Iridium tip is fantastic for resisting fouling and ensuring a stable spark even under high load.

2Pcs CNPAPC Upgrade Double Iridium IX Spark Plugs DCPR7EIX #3144#6046#97637 for 1999-2016 Harley Davidson Twin Cam…

These double iridium plugs take the performance of the standard Iridium IX plugs and boost the durability by using Iridium on both the center and ground electrodes. They are specifically targeted toward the performance enthusiast who wants maximum ignitability and the absolute longest lifespan possible. By maintaining a clean, stable spark, these plugs can actually help you achieve slightly lower fuel consumption because the combustion process is more complete.

Key features that stand out:
* Double Iridium: Offers extreme ignitability and maximum longevity.
* Improved throttle response: Designed for the performance enthusiast.
* Trivalent Metal Plating: Provides enhanced durability and anti-corrosion protection.
* More Fuel Efficient: Stable spark reduces the flameout phenomenon, contributing to lower fuel consumption.

• Pros: Extreme high melting point for demanding engines, exceptional durability and life span, noticeably improved acceleration.
• Cons: Since they are an aftermarket upgrade, cross-referencing compatibility is essential before purchase.
• Best for: Performance-oriented riders seeking the absolute best material for longevity and ignition power in their Twin Cam or XL Sportster.

Expert Opinion: Double iridium is overkill for a casual rider, but if you put serious mileage on your bike or demand top-tier performance, the long-term stability and high melting point make this an outstanding choice.

NGK CR9EIX – Iridium IX Spark Plug – 4-Pack/–

While many Harley riders rely on the DCPR7EIX, certain high-revving or modified engines might benefit from the slightly cooler heat range and different geometry of the CR9EIX. This option is a great choice if you run a setup that requires a different plug specification than the standard Twin Cam fitment. This four-pack provides excellent value and is an authentic NGK product, ensuring quality straight out of the box.

Key features that stand out:
* Genuine NGK Parts: Assurance of original equipment quality.
* Iridium IX Technology: Reliable, long-lasting performance.
* 4-Pack Value: Great quantity for those with multiple compatible bikes or needing spares.
* Direct replacement auto parts: Simple, effective solution for various engine types.

• Pros: Great value in the 4-pack, genuine NGK quality, reliable performance.
• Cons: The CR9EIX specific fitment may not apply to all standard Harley models, so verification is crucial.
• Best for: Owners of motorcycles requiring the CR9EIX specification, or those looking for a bulk purchase of reliable Iridium plugs.

Expert Opinion: Always confirm the exact heat range your manual specifies, especially if your engine is heavily modified. The CR9EIX might be the right answer for specific high-compression V-Twin builds outside the standard Twin Cam application.

E3 Spark Plugs E3.36 Premium Powersports Spark Plug for V-Twin Motorcycles, Harley Davidson Engines, and Other High-Performance Powersport Vehicles, Pack of 1

The E3 spark plug stands out from the competition due to its unique ground electrode design, known as DiamondFIRE Technology. This edge-to-edge electrode promotes a faster and more complete flame kernel expansion, leading to potentially significant improvements in power and fuel economy. For riders interested in minimizing emissions while gaining noticeable performance improvements, the E3.36 offers a truly distinct alternative to traditional designs.

Key features that stand out:
* DiamondFIRE Technology: Patented design delivers a more complete burn, increasing power by up to 12%.
* Lower Emissions: More complete combustion helps reduce CO and hydrocarbon emissions.
* Enhanced Performance: Specifically engineered for high-performance V-Twin engines.
* Universal Fit: Designed to fit a wide range of powersport applications, including late-model Harley Davidson engines.

• Pros: Unique patented design for optimized combustion, potential gains in horsepower and fuel efficiency, helps minimize carbon buildup.
• Cons: Some riders are skeptical about non-traditional electrode designs requiring a learning curve for performance tuning.
• Best for: Riders seeking an innovative alternative to NGK, focusing heavily on maximizing combustion efficiency and lowering environmental impact.

Expert Opinion: The E3 design is certainly non-traditional, but the science behind the focused flame front is compelling. It’s worth testing if your main goal is improved throttle response and measurable fuel economy gains.

NGK DCPR7EIX Spark Plug (2 Pack)

This is the standard, reliable pairing for most modern Harley engines. If you simply want the tested and true performance of NGK Iridium without the bulk of a four-pack or the complexity of specialized plugs, this two-pack is the ideal solution. It is a genuine OEM/OES manufacturer product, guaranteeing that you are installing a high-quality component trusted worldwide.

Key features that stand out:
* Quality Assured: World Wide Leader in spark plug manufacturing.
* OEM/OES Manufacturer: Often specified as original equipment.
* DCPR7EIX Specification: Perfect direct replacement for many Harley models.
* High Quality: Focus on reliable, consistent output and long service life.

• Pros: Absolute standard for quality and reliability, perfect fit for standard replacement, competitively priced for two plugs.
• Cons: Offers standard Iridium performance but doesn’t include the added durability of the double iridium options.
• Best for: The everyday Harley rider who needs a straightforward, reliable, and high-quality Iridium replacement for their regular maintenance schedule.

Expert Opinion: You can’t go wrong with the standard DCPR7EIX from NGK. It’s the definition of a dependable performance plug that improves ignition over copper without unnecessary fuss.

NGK # 6046 Iridium Spark Plugs — DCPR7EIX — Compatible with Harley-Davidson Twin Cam and XL — 4 PCS NEW

This listing provides the popular DCPR7EIX plugs in a convenient and cost-effective four-pack, perfect for the Harley owner who frequently works on their bike or services multiple motorcycles. NGK continually updates its product codes, so recognizing that the 6046 number now corresponds to the newer 97637 is important for proper ordering. As the world’s largest supplier of OEM plugs, NGK ensures that these four plugs offer the best combination of performance and longevity.

Key features that stand out:
* 4 PCS NEW: Excellent bulk value for the reliable DCPR7EIX plug.
* Compatibility: Guaranteed fitment for Twin Cam and XL Sportster models.
* Updated Part Numbers: Clear indication of NGK 97637 (newest number) correspondence.
* Best Combination: Offers reliable performance and longevity in one package.

• Pros: Excellent unit price when buying four, guaranteed OEM quality, versatile fitment across popular Harley models.
• Cons: Four plugs are unnecessary if you only need two for a standard maintenance job.
• Best for: Independent mechanics, shop owners, or Harley enthusiasts who prefer to buy parts in bulk for savings and convenience.

Expert Opinion: For the dedicated DIY mechanic, buying the four-pack is the smartest economic decision. These plugs are a proven staple, offering reliable performance over tens of thousands of miles.

NGK Iridium Sparkplug BPR5EIX-11 for Harley-Davidson Dyna Wide Glide FXDWG/I 1993-1998

Not every great Harley is a modern Twin Cam. This plug specifically addresses the needs of older models, such as the 1993-1998 Dyna Wide Glide. Using Iridium technology in older engines can dramatically improve starting capabilities and acceleration compared to the original copper plugs. The addition of the Platinum disc on the ground electrode also ensures this plug maintains the extreme durability that classic bikes need.

Key features that stand out:
* Model Specific: Perfect fitment for older Harley-Davidson Dyna models.
* Platinum Disc: Welded to the ground electrode for extended long life.
* Trivalent Metal Plating: Provides superior anti-corrosion and anti-seizing properties.
* Performance Improvements: Delivers faster starts and quicker acceleration for classic bikes.

• Pros: Brings modern Iridium performance to classic V-Twins, excellent anti-seizing protection, improved fuel economy over older designs.
• Cons: Limited compatibility; strictly for specific older engine applications.
• Best for: Owners of classic or older Harley models (like pre-1999 Dyna and similar era bikes) looking to modernize their ignition system.

Expert Opinion: Upgrading older ignition systems to Iridium technology is one of the best bang-for-your-buck improvements you can make. It stabilizes the idle and makes those classic motors much more reliable on startup.

Comparison Insights: Choosing the Right Spark Plug

When sifting through these seven options, the choice really boils down to your model and how much you value longevity versus initial cost.

If you ride a modern Twin Cam (1999-2016), the NGK DCPR7EIX series is the proven choice, offering a major reliability bump over standard copper. The DCPR7EIX (2 Pack) is your standard maintenance buy, while the 4 PCS NEW pack is better value if you service bikes regularly.

For riders who prioritize absolute maximum life and fuel efficiency, the CNPAPC Double Iridium plug provides next-level durability, though it comes at a premium.

If you own a classic Harley, look specifically for the NGK BPR5EIX-11 to ensure you get the right heat range and size for older heads, bringing modern ignition reliability to vintage V-Twin performance.

Finally, the E3 Spark Plug is the best option if you are keen to experiment with non-traditional electrode geometry and potentially gain marginal improvements in horsepower and throttle response due to its complete combustion design.

Final Verdict: Which Plug Sings the Loudest?

Choosing the best spark plugs for Harley Davidson depends entirely on your bike’s age and your riding goals.

For the Best All-Around Performance and Reliability: The winner is the NGK DCPR7EIX (either the standard pair or the 4-pack). This plug provides the best balance of advanced Iridium technology, proven compatibility with the Twin Cam engine, and long-term durability that most riders expect.

For the Durability King: If money is no object and you want the plug that lasts the longest, opt for the CNPAPC Double Iridium IX. Its construction is simply superior in terms of material resistance to heat and fouling.

For the Classic Bike Enthusiast: The NGK BPR5EIX-11 is essential. Don’t try to fit a modern plug into a classic application; using this specific model guarantees the ignition upgrade without risking damage.

Best Spark Plugs For Harley Davidson FAQ

Q1: Why should I upgrade my Harley Davidson spark plugs from standard copper to Iridium?

Upgrading to Iridium spark plugs, like the popular DCPR7EIX, offers several critical benefits. Iridium has a much higher melting point than copper, allowing the electrode to be much finer. This results in a consistently hotter, more focused spark which improves engine performance, reduces the chance of misfires, particularly at high RPMs, and significantly extends the service interval compared to copper plugs.

Q2: What is the correct spark plug gap for a Harley Davidson Twin Cam engine?

While many premium plugs like the NGK Iridium IX come pre-gapped, it’s always best to check. For most Harley Davidson Twin Cam and Evolution engines, the standard recommended gap is between 0.038 and 0.042 inches. Always consult your motorcycle’s owner’s manual for the exact specification, especially if you have high-performance ignition components installed.

Q3: Does the heat range of the spark plug really matter for V-Twin performance?

Yes, the heat range (like the ‘7’ in DCPR7EIX) is crucial. It dictates how quickly the plug can transfer heat away from the combustion chamber. Using a plug that is too hot can cause pre-ignition (pinging) and engine damage, while a plug that is too cold can lead to fouling. Most stock Harley engines require a medium-to-hot plug for optimal street use, but heavily modified or high-compression engines may need a cooler plug (a higher number, like the CR9EIX) to prevent overheating.

Q4: How often should I change my Iridium spark plugs in my Harley?

While Harley Davidson may recommend changing standard plugs frequently, high-quality Iridium plugs are built to last much longer. Typically, Iridium plugs are good for at least 30,000 to 40,000 miles in a standard Harley V-Twin before performance degradation is noticeable. However, if you experience rough idling, poor fuel economy, or Harley misfires, check them sooner.

Q5: What is the difference between Single Iridium and Double Iridium plugs?

Single Iridium plugs use the durable material only on the center electrode. Double Iridium plugs (like the CNPAPC option reviewed) use Iridium on both the center electrode and the tip of the ground electrode. This dual application offers superior erosion resistance and is designed to provide maximum longevity and stability, making them ideal for performance engines.

Q6: Can I use E3 plugs in my older Harley, and do they improve fuel economy?

E3 plugs, with their DiamondFIRE design, are generally compatible with a wide range of powersport applications, but you must ensure you select the correct thread size and heat range (like the E3.36 for V-Twins). Many riders report noticeable improvements in throttle response and anecdotal evidence of slightly better fuel economy, attributed to the more complete, cleaner burn promoted by their unique electrode geometry.